The present invention relates generally to an automated measurement and documentation system, in particular, to a method and apparatus for automated measurement and documentation of crash scenes.
Crash scene analysis is performed to determine the causes and circumstances of crashes in order to make the transportation mode safer in the future, and to determine criminal and civil liability. The position and orientation of vehicles, vessels, aircraft, and their pieces relative to each other and the scene features is important in attempting to determine the crash dynamics and cause.
Currently, crash scene measurements are done manually with wheel and tape measures. The data are recorded by hand and the analysis is done through manual calculation. The results of the measurements and calculations are captured on hand drawn sketches. The scene elements can only be located relative to each other and any nearby landmarks. Scene measurements are two dimensional, providing only a projection of the scene on an artificially flat landscape. Usually it takes more than one person to survey a crash scene; a helper holds the end of the tape and helps record measurements. The hand drawn sketches are not in a standard format making it very difficult to correlate multiple incidents, store the data, and transmit the data. Although the crash scene researchers are well trained, the number of manual operations in the measurement and analysis are a source of inefficiency and errors.
To improve its processing of these important data, the present invention will automate the process, and provide accurate, rapid, crash scene measurement, analysis, and documentation. The present invention will require only one documenter and provide for much faster scene measurement and documentation, which will minimize the labor cost. The present invention will maximize measurement accuracy while minimizing measurement errors by automatically recording precise Global Positioning System (GPS) measurements and providing step-by-step process prompts to the user. Unlike manual scene documentation, the measurements are made in a universal coordinate system that has well known transformations to local datums. This allows the absolute position of the scene to be located even where there are no reference landmarks such as in the desert, and provides for the possibility of recreating the scene in the future at the proper position and orientation. The data are three-dimensional allowing much more accurate scene documentation. Unlike the manual methods, the present invention automates the scene position and dimension calculations, as well as the scene drawing so that it provides, in near real-time, the accident scene report and accurate graphical representations of the scene. This reduces analysis errors, report preparation time, as well as providing a standard report format and data file format. The standard data file format will provide for electronic storage, retrieval, and transmission to facilitate data analysis and multiple incident correlations.
The present invention has a user-friendly interface, and provides for data and report security. To reduce training costs the user-friendly interface incorporates procedure prompts, and check for data entry errors and missing data. However, as much as possible, the Graphical User Interface (GUI) is based on the current procedures to minimize researcher retraining. The present invention is designed to be a low cost augmentation to a potable computer (palmtop or laptop).
Similar but much different systems based on GPS have been designed for construction and land surveying. These previous systems are designed to work over a much larger area than the instant device, and are more cumbersome to use. The present invention is tailored to crash scene and similar applications requiring accurate, local scene measurement and documentation. It makes use of unique processing and interface software to maximize efficiency and accuracy.
The present invention""s processing software does not require determination of the unmeasurable GPS carrier phase cycles between the reference module and the measurement module using a solution space search strategy or statistical selection as prior systems require. As determining these cycles is the greatest cause of processing error in these systems, the present invention has greater solution integrity and accuracy over its smaller operational area.
The present invention""s processing software has a unique configuration that provides enhanced solution integrity by combining an extended Kalman filter with a least-mean-square initialization and figure-of-merit determination process. The configuration provides for unique, robust measurement validation and selection, as well as position accuracy enhancement. It also provides an automatic means of recovery in case the Kalman Filter begins to diverge from the true solution.
The present invention""s unique multimedia user interface provides process prompts and error checking tailored to the crash scene application. For instance, the automotive crash scene system conforms to the US Department of Transportation""s Model Minimum Uniform Crash Criteria for scene documentation. The user is prompted to take all measurements and other data required by this standard, and the report produced conforms to the standard. To aid the single user, the present invention""s prompts and instructions are given both graphically and audibly. The present invention also can be configured to respond to spoken commands instead of keystrokes to keep the user""s hands free.
The previous systems make use of expensive proprietary hardware and software. The present invention leverages low cost, commercially available hardware, and commercial Computer Aided Drafting (CAD) and word processing software to provide enhanced functionality at about one twentieth the cost of the previous total solution, survey systems on the market.
Such an invention is needed by automotive, marine, and aircraft crash investigators because of it is more accurate, efficient, and standardized than the current manual systems. It requires less personnel, saving labor costs, and its instructive and error checking interface reduces training costs and enhances measurement integrity. It also can be produced at a low cost that allows more high quality, crash scene research to be performed on the same budgets, ultimately improving the safety of all modes of transportation.
The present invention consists of two modules, the measurement and reference modules. The measurement module is used by the scene surveyor to measure the crash element points while the reference module""s GPS measurements are used to remove common errors from the measurement data.
The reference module has a portable computer, either a commercial-off-the-shelf (COTS) laptop, palmtop, or pen computer. A COTS GPS receiver board is either integrated in the computer package or packaged separately. It communicates with the receiver through a digital I/O port, most often a serial port. The computer contains the turn-key invention software that uses a Graphical User Interface (GUI) and audio to guide the user through a scene measurement. The software also controls the GPS receiver, collects the GPS data, processes the data, builds a Computer Aided Drafting (CAD) scene file, calls a COTS word processing program and writes a report, and calls a COTS CAD program to draw the scene. The GPS receiver requires a COTS antenna for receiving the GPS signals. In the present invention, the antenna is mounted on survey stake with a bubble plumb/level or electronic level sensor, and is placed on points whose positions define the relative shape, orientation, and size of the scene elements.
The reference module consists of a COTS GPS antenna and receiver integrated with a microcontroller board and power supply. The microcontroller controls the receiver and stores the GPS reference data. The reference module is placed for convenience. Normally, a silver dollar sized antenna with a magnetized bottom will be stuck to the roof of the surveyor""s vehicle and the electronics are in the vehicle but the reference module could be placed anywhere near the crash scene.
The device can include optional equipment to enhance its capabilities. In some versions of the present invention, a COTS radio link between the reference and measurement modules will allow real-time scene dimensions to be calculated. A wireless Internet modem or a Cellular Digital Packet Data (CDPD) modem can be used to connect from the field to a central computer to send the completed documentation or retrieve needed data or assignments. Other optional equipment can include a COTS digital camera for pictures of the scene and a laser range finder. The low cost, laser range finder may be useful for measuring distances under overpasses or in tunnels where GPS satellite visibility is limited.
Using the present invention, a single surveyor can accurately and rapidly, measure and document a crash scene. To perform the crash scene measurements, the researcher powers up the pen or laptop computer, and initiates the turnkey software. The turnkey software features a user friendly, graphical interface that can provide step-by-step prompts, if the user desires. This software automatically will start a Built-In-Test (BIT) systems check, set up the GPS receiver, and initiate measurement collection.
The user will be prompted to initialize the crash scene record with a name, location designation, and any other general information desired. The researcher will be asked about the number and type of vehicles, vessels, or aircraft involved, and about other scene elements. Then they will measure the crash scene by walking to each point in the crash scene for which they want a measurement, and placing the survey antenna stake there for about five seconds. At each point, they will select a measurement type (car 1xe2x80x94right front corner; skid mark 1xe2x80x94start point; etc). The software will automatically record the GPS measurements for each point so no manual mistakes are possible. Each common, crash scene element will have a minimum number of points to be measured. If the researcher misses a measurement point or entire element, the software will remind him/her. The user will have the opportunity to annotate the scene record and scene elements before, during, and after the measurement process. Also, the user can modify, delete, or repeat a measurement during and after the measurement process. Upon completing the measurements, the processing and report software is initiated.
The reference measurements are either constantly collected from a radio link between the reference and measurement units or the user can connect the measurement computer to the reference module via standard computer I/O cable (RS-232, RS-422, parallel, USB, etc.) or infrared link. The reference measurements are automatically retrieved from the reference module and stored on the computer. Then the present invention""s processing software will take the raw GPS data from both receivers and determine the relative position of each point to about centimeter accuracy, and angles between line segments to about a tenth of a radian accuracy. (Angular accuracy depends on the distance between points with better accuracy for widely separated points.) Each GPS measurement provides a three-dimensional position offset from the reference point (North, East, and Altitude; Latitude, Longitude, and Altitude; Earth Centered Earth Fixed (ECEF) x, y, z; etc.). Absolute position is improved by using a DGPS correction from a national DGPS system or by locating the reference unit at a geodetic marker.
The software of the present invention then automatically develops a CAD quality graphical representation of the scene by formatting a drawing file that can be used by a COTS CAD program. These graphical scene elements will be scalable to accurately represent the relative size and orientation of the actual scene elements. The graphic file of the crash scene will be digital so it can be readily stored, manipulated, and transmitted. It also could be developed as a three dimensional graphic that could be rotated to provide a view from any angle.
The software of the present invention will then call a COTS word processing program, and specify a report template from a preformatted library of the most common crash types. A generic report template also will be available for less common types of crashes. The scene data from the scene measurements and the researcher""s input will automatically be entered in the proper fields of the report. The user then either accepts that report, augment it, or access a summary of the processed data and create a report to their tastes. If they elect to edit the automated report, they will have access to the full functionality of the word processor.
The present invention is engineered to cost an order of magnitude less than a general GPS survey system with the same accuracy level, which is not tailored to the applications identified above. Although the present invention will cost more than a manual survey (measuring tape and wheel), its efficiency and enhanced capabilities will produce savings that will quickly recoup the investment. The specifics of the application process are embedded in the user interface, which reduces training requirements, survey time, and report preparation time. With the present invention, scene measurement and documentation could be performed with little training in the mechanics of the scene survey. It also will increase productivity through enhanced report accuracy and integrity, and facilitating more efficient and productive analysis. The measurements are automatically recorded and the positions calculated relative to the reference point regardless of the measurement order. No line-of-sight is required between any points for the GPS measurements. The resulting data and documentation will be in electronic format for easy storage, transmittal, and analysis.
The measurement process can be very fast if required for the safety of the researcher or the convenience of the public. A crash scene consisting of two vehicles (12 points including deformation points), a set of skid marks (four points) and the absolute position (Lat., Long, Alt.) of the reference point will take approximately four minutes to measure. This duration includes fifteen seconds to walk between points so only a total of 80 seconds is spent actually at the points.